OK, das ist echt interessant, ich konnte mir auch gleich vorstellen, dass D und E beide vom lateinischen "obligare" stammen, und dachte sofort dass die deutsche Schreibweise "eingedeutscht" sei (analog zu "liegen"), nun behauptet der Duden http://www.duden.de/rechtschreibung/obliegen
aber, die Herkunft stamme von
"mittelhochdeutsch obe ligen, althochdeutsch oba ligan = oben liegen, überwinden"
Der OED schreibt zum Englischen, auch interessant:
Etymology: < Anglo-Norman obliger, oblijer and Old French, Middle French obliger, obligier to bind by oath or promise, pledge (mid 13th cent.; also reflexive), to constrain, force (c1485), to make liable (1538; also reflexive), to perform a service, give pleasure (1538) < classical Latin obligāre to bind by an oath, promise, or moral or legal tie, to pledge, mortgage, to make liable, to bind or tie around, bind up, restrain < ob- ob- prefix + ligāre to tie, bind (see ligate v.).
The word was formerly pronounced /əˈbliːdʒ/ , as noted by 17th- and 18th-cent. orthoepists including Coles, Strong, and Young, and this pronunciation is recorded as a variant up until the early 19th cent., e.g. in Walker (1806). It appears to have become obsolete by the mid 19th cent., and is not found in later sources, including Webster (1828), Smart (1857), Worcester (1860), and Stormonth (1884). Webster (1828) includes the comment that the word is ‘pronounced as written, not obleege’, which perhaps implies that /əˈbliːdʒ/ , while deemed incorrect, could still be heard at this time. The Imperial Dict. (1883) records an obsolete pronunciation /ɒˈbliːdʒ/ .
H. C. Wyld, in Hist. Mod. Colloq. English (ed. 3, 1936) 226, concludes from the following quotation that in the mid 18th cent. /əˈblaɪdʒ/ was a colloquial pronunciation which received some criticism, while another pronunciation, perhaps /əˈbliːdʒ/ , was perceived as more correct:
1749 Ld. Chesterfield Let. 27 Sept. (1932) IV. 1407 Even his [sc. a vulgar man's] pronunciation of proper words carries the mark of the beast along with it... He is obleiged, not obliged, to you.
Modern French is likely to have influenced pronunciation of the word as /əˈbliːdʒ/ , especially during the 17th and 18th centuries. However, it has also been suggested by Luick that this pronunciation may have developed within English (see discussion in E. J. Dobson Eng. Pronunc. 1500–1700 (ed. 2, 1968) II. §138 (3)).
In Middle English occasionally with prefixed past participle (compare y- prefix).